High-entropy silicide superconductors with W5Si3 -type structure

We report the synthesis, crystal structure, and physical properties of two new high-entropy silicides (HESs), namely ${({\mathrm{Nb}}_{0.1}{\mathrm{Mo}}_{0.3}{\mathrm{W}}_{0.3}{\mathrm{Re}}_{0.2}{\mathrm{Ru}}_{0.1})}_{5}{\mathrm{Si}}_{3}$ and ${({\mathrm{Nb}}_{0.2}{\mathrm{Mo}}_{0.3}{\mathrm{W}}_{0.3}{\mathrm{Re}}_{0.1}{\mathrm{Ru}}_{0.1})}_{5}{\mathrm{Si}}_{3}$. Structural analysis indicates that both HESs consist of a (nearly) single tetragonal ${\mathrm{W}}_{5}{\mathrm{Si}}_{3}$-type phase (space group $I4/mcm$) with a disordered cation distribution. Electrical resistivity, magnetic susceptibility, and specific heat measurements show that ${({\mathrm{Nb}}_{0.1}{\mathrm{Mo}}_{0.3}{\mathrm{W}}_{0.3}{\mathrm{Re}}_{0.2}{\mathrm{Ru}}_{0.1})}_{5}{\mathrm{Si}}_{3}$ and ${({\mathrm{Nb}}_{0.2}{\mathrm{Mo}}_{0.3}{\mathrm{W}}_{0.3}{\mathrm{Re}}_{0.1}{\mathrm{Ru}}_{0.1})}_{5}{\mathrm{Si}}_{3}$ are weakly coupled bulk superconductors, which represent the first superconducting high-entropy nonoxide ceramics. In particular, these HESs have higher ${T}_{\mathrm{c}}$ values (3.2--3.3 K) compared with those of the binary counterparts and their ${B}_{\mathrm{c}2}(0)/{T}_{\mathrm{c}}$ ratios are the largest among superconductors of the same structural type.